This invention relates to a linear guide device, and more particularly to a mechanism for preventing guide rails from displacing sidewards in the linear guide device (hereinafter referred to as "a guide rail sideward displacement preventing mechanism", when applicable).
In general, in a linear guide device, its guide rail is extended axially and has ball rolling grooves in both sides which are also extended axially, and its slider is engaged with the guide rail through a number of rolling balls. The linear guide device thus constructed is fixedly mounted on a flat mounting surface of a machine tool or industrial machine. For instance, the guide rail is mounted on the upper surface of a machine bed with bolts, and the slider is secured to the lower surface of a machine table with bolts. However, when the slider is greatly shocked in a lateral direction, then it may be displaced laterally. In order to overcome this difficulty, as shown in FIG. 6 a stepped surface D is formed in the machine bed 3, and with one side of the guide rail 1 on the stepped surface D, the guide rail 1 is pushed against the stepped surface D with a lateral push plate 5 so that the guide rail 1 is prevented from being shifted laterally.
In this case, the stepped surface D must be high in straightness, because it is necessary that the machine table guided linearly through the slider 2 by the guide rail 1 is moved with high precision; that is, it is rather difficult to machine the stepped surface D to meet the above-described requirement. In general, a machine table is guided by two guide rails. Therefore, the two guide rails must be in parallel with each other. And formation of two stepped surfaces results in an increase in manufacturing cost. In addition, it is, of course, necessary to form the lateral push plate 5, and in order to mount the latter 5 on the machine bed, it is necessary to use a number of mounting bolts, and to form a number of tapped holes in the machine bed 3 for the mounting bolts. Thus, it takes a lot of time and labor to install the guide rails.
In order to eliminate the above-described difficulties, for instance Japanese Utility Model Application (OPI) No. 147927/1988 and Japanese Patent Application (OPI) No. 156633/1988 have proposed methods of preventing a guide rail from displacing laterally. In the former method, a plurality of elongated stripe-like protrusions are formed on the mounting surface (or lower surface) of the guide rail in such a manner that they are extended longitudinally, to resist against the lateral displacement of the guide rail. On the other hand, in the latter method, a dovetail groove is formed in the base surface, and the guide rail is fixedly secured therein with bolts, and gaps between the guide rail and the dovetail groove are filled with a molding material, and the latter is solidified.
Those methods are simple, and are intended to prevent the lateral displacement of the guide rail without formation of the stepped surfaces which must be high in precision. However the former method in which the mounting surface of the guide rail is made uneven is disadvantageous in that it is impossible to positively fixedly secure the guide rail. On the other hand, the latter method, in which the dovetail groove is formed in the base surface, is intended to increase the rolling guide damping effect, and is disadvantageous in that it is rather difficult to machine the dovetail groove or to form the rail, which results in an increase in manufacturing cost. In addition, the rail is high, and therefore the guide rail is liable to be bent when subjected to thermal treatment.